Deep Brain Stimulation (DBS) is a surgical procedure used for the treatment of various diseases including Parkinson's disease and essential tremor. In the surgical procedure, a DBS lead is implanted at a target site to stimulate brain matter and thereby alleviate the clinical condition. To be effective and avoid deleterious side effects, the DBS lead must be located correctly within the brain matter. Therefore, before DBS lead placement is made, microelectrodes are typically used to penetrate deep brain matter and refine anatomical or imaging-based stereotactic targeting techniques. The microelectrode recording is used to precisely identify the target (i.e. thalamus, sub-thalamic nuclei (STN), GPi) in the brain for test stimulation before DBS lead placement is made. This recording involves a small metal wire, namely the microelectrodes recording leads (MER lead) that monitors the activity of nerve cells in the target area. Through the recording, the surgeon listens to the contrast in the electrical signal fired by the neurons and reads the waveforms on a computer to identify the stimulation target. The size of the MER lead is made extremely small to prevent bleeding and damage to the human brain as it is inserted deep into the human brain.
Currently, MER leads and stereotactic image guided systems (e.g. Nexframe® stereotactic image guided system by Medtronics) are the only tool the surgeon uses to locate the stimulation target. Intraoperative CT scans to augment information provided by preoperative MRI scans have been put forward to provide more accurate navigation of the MER. However, no intra-operative imaging device is currently available to provide real time images to the surgeon. In addition, the target for stimulation is typically very small (eg. for STN 3 to 5 mm), which makes it difficult to locate if the brain shifts during surgery. If the initial path of the MER lead is offset such that the stimulation target is missed, the surgeon will typically pull back the lead and reinsert it a few millimeters away with no indication or guidance from any devices on what direction and distance to re-target the lead. This method is suboptimal and can cause significant damage to the brain. Reinserting the probe multiple times into a similar region of the brain causes increasing risk of excessive bleeding which causes brain damage as well as affecting stimulation effectiveness.